With a recent increase in storage capacity required for storage devices, mechanisms for virtually allocating physical resources, including disks, have been received attention. In Thin Provisioning, one of such mechanisms, no correlation is made between a logical volume and a physical disk at the time of creation of the logical volume. The physical disk of a storage pool is dynamically allocated only when data is actually written by a host.
In order to release the allocated physical volume in Thin Provisioning, the entire logical volume may be initialized or a certain area of the logical volume may be released specified by, for example, logical block address (LBA) in accordance with an initialization command issued by a host or other component.
In Thin Provisioning, it is assumed that a host or other component issues an initialization command for a larger range than a normal I/O range during release of allocated physical volumes. In a copying function in which snapshots of a logical volume are created on an on-demand basis, however, data is written and the logical volume is released typically after areas corresponding to the copy source volume are synchronously copied to a copy destination volume during execution of an I/O or an initialization command for uncopied areas.
As described above, since the copying process and the releasing process are performed asynchronously in response to the initialization command issued with respect to the logical volume to be copied on an on-demand basis, a response process indicating the releasing process has been completed may be delayed and the response may be degraded.
Japanese Laid-Open Patent Publication No. 2007-310861 and Japanese Laid-Open Patent Publication No. 2006-48300 are examples of related art.